The present invention relates to a push switch which can present a two step switching operation by pressing it and finds applications in various kinds of electronic equipment such as video cameras, video cassette recorders, facsimile machines and the like.
In recent years as a multiple function is required more and more of many kinds of electronic equipment, demands for a push switch capable of performing the two step switching operation have been increasing.
With this type of switch, when its push button is lightly pressed by finger touching, a first switching mechanism is actuated and subsequently when the push button is further pressed, a second switching mechanism is actuated.
In its typical application, the first switching step is used for getting a certain function of electronic equipment into a preparatory mode and the second switching step is used for getting that specific function into a full operational mode.
A more detailed description of the prior art push switches of the kind mentioned above is given in the following:
FIGS. 1(a)-1(c) is a partially cross-sectional view of one switch element of the typical prior art push switch.
In FIGS. 1(a)-1(c) an insulative substrate has disposed thereon one or more switch elements.
One switch element disposed on the insulative substrate 1 comprises a first pole contact 2 shaped like a "C" letter, a second pole contact 3 shaped like another "C" letter and disposed inside the first pole contact 2, a third disc shaped pole contact 4 disposed inside the second pole contact 3 and conductor leads (not shown) connected to these pole contacts 2, 3 and 4, respectively.
Over the first pole contact 2 and the second pole contact 3 are placed an upper side diaphragm 5 and a lower side diaphragm 6, respectively, which are dome shaped and made from an electro-conducting and elastic metal.
The upper side diaphragm 5 is covered by a insulating membrane 7 and fixed to the first pole contact 2, and also the lower side diaphragm 6 is fixed to the second pole contact 3 by soldering and the like to complete the switching element.
Further, over the upper side diaphragm 5 is disposed a push button 8, movement of which is guided by a panel 9 placed above the switch element.
Next, the operation of this push switch will be explained.
When the push button 8 is pressed lightly by a finger, the upper side diaphragm 5 will come in touch with the lower side diaphragm 6 to make contact between the first pole contact 2 and the second pole contact 3 as shown in FIG. 1(b), causing a first switching operation to take place.
Then, when the push button 8 is pushed strongly further, the lower diaphragm 6 will come in touch with the third pole contact 4 as shown in FIG. 1(c) to make contact between the second pole contact 3 and the third pole contact 4, causing a second switching operation to take place. When the finger pressure is removed from the push button 8, the diaphragms 5 and 6 will return to their original shapes as shown in FIG. 1(a) by their elastic springback force to break contact between the pole contacts with a resultant cancellation of the first and second switching operations.
In the above prior art example, a push switch of applying pressure to diaphragms through a push button was presented but also there is a push switch type wherein the diaphragms are pressed directly by a finger without using the push button.
However, the conventional push switches as described in the foregoing require two diaphragms to make one switch element, resulting in such problems as too many component parts required, a complicated assembly process due to a high mechanical precision needed in positional alignments of diaphragms and a likelihood of ending up with a high production cost.